Method of and apparatus for producing paper pulp



June 30, 1936. F. w. ADAMS ET AL 2,045,813

METHOD OF AND APIARATUS FOR PRODUCING PAPER PULP Filed June 26,- 1934 2She ets-Sheet 1 Egi ' June 30, 1936. I F. w, ADAMS ET AL 2,045,818

METHOD OF AND APEARATU S"FOR PRODUCING PAPER PULP Filed June 26, 1954 2Sheets-Sheet 2 //\/l/ENTORSI -%4'ATTORNE Patented June 30, 1936 METHODOF AND APPARATUS FOR PRODUCING PAPER PULP Frederick W. Adams, Stoneham,Mass, and George S. Witham, Jr., Lincoln, N. H.

Application June 26, 1934, Serial No. 732,456

8 Claims.

This invention relates to the production of chemical woodpulp. It hasfor its general objects to improve the quality of the pulp obtained froma given grade of wood, and to effect economies in the pulp producingprocess.

As is well understood by those skilled in this art, the commercialmethods of producing pulp of this character include the cooking of woodchips in a large digester. At the completion of the cook, the pulp anddigester liquor are discharged into a pit or vat, the dischargingoperation being commonly referred to as 'blowing the digester, and thepit or vat usually being called a blow pit. When the charge is ready tobe blown, it is under considerable pressure, say for example, between 40and 120 lbs. per square inch, and its temperature is high, ranging from,perhaps, 270 to 350 F. The blowing operation consists simply in openingthe blow valve and allowing the pressure in the digester to force theentire charge through a pipe line into the blow pit, where the pressureis substan tiallyatmospheric. Consequently, when the pulp is discharged,the pressure on the fibers is released very quickly. This sudden releaseof pressure produces an effect on the fibers similar to that purposelycreated in a similar manner in some industries for the purpose ofexploding the product under treatment. In the case of pulp, however, theresult is to weaken the fiber and, consequently, to reduce the strengthof the paper ultimately made from the fiber.

In addition to this effect, the practice just described also results inproducing large volumes of steam which are discharged into thesurrounding atmosphere through the vomit stack leading from the blowpit. Small proportions of sulphurous acid are carried ofi with the steamand gases so evolved and create a nuisance, due partly to theirdisagreeable smell and partly, also, to their tendency to attack metalroofings and other exposed metal parts of adjacent buildings.

The present invention is especially concerned with these considerations,and it aims to improve processes of handling the pulp in connection withthe cooking operation with a view to avoiding the objections justdescribed and conserving the heat contained in the cooked charge, andwhich, according to the customary process, is wasted.

The nature of the invention will be readily understood from thefollowing description when read in connection with the accompanyingdrawings, and the novel features will be particularly pointed out'in theappended claims.

In the drawings,

Figure 1 is a side elevation, partly in section, showing somewhatdiagrammatically those features of an apparatus with which thisinvention is-more especially concerned;

Fig. 2 is an end view on a larger scale of the 5 float operated valveillustrated in Fig. 1; and

Fig. 3 is a vertical, sectional view of parts of the apparatus shown inFig. 1.

The apparatus illustrated in the drawings comprises a digester 2, fromthe bottom of which the usual pipe line or blow line 3 leads into theblow pit 4. Included in the blow line is the usual blow-oil valve 5. Sofar as these features of this arrangement are concerned, they may be ofany usual or convenient'iorm. According to the present invention, aninjector 6 is included in the blow line 3, and the intake leg 1 of thisinjector leads into a well or reservoir 8 which iskept constantly filledto a substantially predetermined level with cold water the valve fails,for any reason, to operate properly.

When the cook has been completed and the valve 5 is opened to blow thecharge, the kinetic energy of the outgoing mixture of pulp and wastedigester liquor flowing through the injector creates a suction in theintake leg 1, serving to cause a flow of water from the well 8 throughthe leg 1 and into the injector where it becomes mixed with the pulp anddigester liquor flowing through the pipe line 3. By selecting aninjector of a design and capacity suited to the requirements of theindividual digester with which it is to be used, and properlycontrolling the head through which the cooling water must be raised, Ithe proportion of water mixed with the outgoing charge can bepredetermined within limits surficiently accurate for all practicalpurposes. The quantity of water so mixed with the discharged stockshould be sufficient to prevent the forma tion of any objectionablequantity of steam during practically the entire blow. When the valve 5is first opened there is a brief instant during which the dischargedstock will not be mixed with water, but this interval of time is onlymomentary, as will readily be appreciated, and is simply long enough toenable the flow of stock to set up the necessary vacuum required tostart the flow of water through the injector. There; after the stockwill be dischargedinto the blow pit in a hot condition but at atemperature below the boiling point'of water. With this arrangement,therefore, the explosion of the fiber, and the consequent weakeningaction on it, is avoided and the creation of large volumes of steam alsoare prevented.

The mixing of the water with the discharged stock serves not only tocool the pulp, as above described, but it also initiates the pulpwashing operation, the water added to the stock being utilized for thispurpose. In addition, it permits the washing of the pulp at a highertemperature than that ordinarily used so that this operation is mademore effective, more uniform, and proceeds more rapidly. Thus the heatwhich has been wasted by former processes is conserved and made toservea useful purpose.

The foregoing operations are typical of those used in the production ofchemical wood pulp by the sulphite process. The invention is equallyapplicable to the sulphate and soda processes. In the latter, however,the water usually will be replaced with black liquor. Here, theinvention produces the additional advantage of assisting in theevaporation of the water constituent of the liquor incidental to theusual recovery process.

Preferably a check valve [4, Fig. 3, is located at the intake port ofthe injector, or at some point in the intake leg 'I, where it willprevent any flow downwardly through this leg.

While we have herein shown and described a procedure embodying thisinvention which is typical of one process of producing pulp, and anapparatus suitable for use in said process, it will be evident that theinvention may be embodied'in other forms and practiced in other wayswithout departing from the spirit or scope thereof.

Having thus described our invention, what we desire to claim as new is:

1. The combination with a pulp digester, a blow-off line leadingtherefrom and a blow-off valve in said line, of means for mixing asumcient quantity of a suitable liquid with the charge of stock andwaste liquor while the stock is flowing through said lineto prevent anysubstantial explosion of the fiber as the latter is discharged from saidline.

2. The combination with a pulp digester, a

blow-oil line leading therefrom and a blow-ofl valve in said line, ofmeans for mixing a sum-- cient quantity of a suitable liquid with thecharge of stock and waste liquor while the stock is flowing through saidline to prevent the discharge of anysubstantial quantity of steam fromsaid line during the blowing of a charge.

3. The combination with a pulp digester, a blow-oi! line leadingtherefrom and a blow-off valve in said line, of an injector in saidline, and 10 a supply of relatively cool liquid with which the intakeleg of said injector is connected.

4. The combination with a pulp digester, a blow-off line leadingtherefrom and a blow-oil valve in said line, of an injector in saidline, and 15 7 means for conducting relatively cool liquid to the intakeport of said injector.

5. The combination with a pulp. digester, ablow-off line leadingtherefrom and a blow-off valve in said line,of an injector in said line,a '20 well for holding a supply of relatively cool liquid, an intakepipe leading from the intake port of said injector into said well, and acheck valve in said pipe serving to prevent any substantial flow ofliquid through the pipe from the injector to. the well.

6. That improvement in methods of producing chemical wood pulp, whichconsists in cooking the pulp, blowing the charge at the end of the cook,and causing the kinetic energy of the charge to mix a cooling liquidwiththe outgoing charge before the charge is liberated.

7. That improvement in methods of producing chemical wood pulp, whichconsists in cooking the pulp, blowing the charge at the end of the cook,and causing the kinetic energy of the charge to mix a suiiicientproportion of a suitable cooling liquid with the outgoing charge, while4 said charge is still under pressure, to substantially prevent thedischarge of steam at the final delivery. 7

8. That improvement in methods of producing chemical wood pulp, whichconsists in cookin the pulp, blowing the charge at the end or the cook,and, during said blowing operation mixing a suflicient proportion ofrelatively cool liquid with the stream of pulp 3am discharged to preventexplosion of the fiber upon its final delivery. FREDERICK W. ADAMS.

GEORGE S. WI'I'HAM, Jn.

